What is GMT (Greenwich Mean Time)?
Greenwich Mean Time is the mean solar time at the Royal Observatory in Greenwich, London. It equals UTC+0 and is the time the UK keeps in winter.
What is Greenwich Mean Time?
Direct answer. GMT is the time at the Prime Meridian (0° longitude), which runs through Greenwich in London. It is the reference point from which every other time zone is measured, and equals UTC+0.
Historically GMT was the world’s time standard, set by the stars from the Royal Observatory. Today the global standard is UTC, kept by atomic clocks, but the UK’s winter clock is still called GMT. In summer the UK moves one hour ahead to British Summer Time.
Key fact: GMT = UTC+0. It is UK winter time and the origin line for the world’s time zones.
FAQ
Is GMT the same as UTC?
For everyday purposes they are the same — both are UTC+0. Technically UTC is a precise atomic time standard while GMT is the older astronomical time at the Greenwich meridian, but for clocks and timetables the difference is negligible. More on UTC →
Is the UK always on GMT?
No. The UK is on GMT in winter and on British Summer Time (UTC+1) in summer. GMT vs BST →